发明申请
US20100252147A1 HIGH-STRENGTH COLD-ROLLED STEEL SHEET 有权
高强度冷轧钢板

HIGH-STRENGTH COLD-ROLLED STEEL SHEET
摘要:
The invention provides a high-strength cold-rolled steel sheet which is improved in elongation and stretch-flangeability and exhibits more excellent formability. The high-strength cold-rolled steel sheet has a composition which contains by mass C: 0.03 to 0.30%, Si: 0.1 to 3.0%, Mn: 0.1 to 5.0%, P: 0.1% or below, S: 0.005% or below, N: 0.01% or below, and Al: 0.01 to 1.00% with the balance consisting of iron and unavoidable impurities. The high-strength cold-rolled steel sheet has a structure which comprises at least 40% (up to 100% inclusive) in terms of area fraction of tempered martensite having a hardness of 300 to 380 Hv and the balance ferrite. The cementite particles in the tempered martensite take such dispersion that 10 or more cementite particles having equivalent-circle diameters of 0.02 to less than 0.1 μm are present per one μm2 of the tempered martensite and three or fewer cementite particles having equivalent-circle diameters of 0.1 μm or above are present per one μm2 of the tempered martensite.
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